feat(work): auto-tick epic story bullets when a story finishes

- Add tickStoryBulletInEpic(workRoot, epic, story) helper that finds
  the bullet in the parent epic's `## Stories` section linking to the
  given story folder and flips `- [ ]` to `- [x]`. Idempotent.
- applyApprovedState now ticks the parent epic bullet whenever a
  story flips to status: done (alongside the existing per-task tick
  and epic-status flip). Epic file gets staged on either ticked-or-
  flipped, not just flipped.
- Backfill all 3 existing epics: 21 bullets ticked to match their
  already-done story statuses (binder-wrap-helper x3, library-
  evaluation-policy x9, ci-security-and-supply-chain x9).

docs/work/2026-05-14-ci-security-and-supply-chain/_epic.md

@@ -18,12 +18,12 @@ The repo's security posture has zero security tooling. ADR-022 + the library-eva
 
 ## Stories
 
-- [ ] [01 — Trace schema extensions (socketRisk + lastRevalidated)](01-trace-schema-extensions/_story.md)
-- [ ] [02 — Socket integration (skill + CI)](02-socket-integration/_story.md)
-- [ ] [03 — Renovate adoption](03-renovate-adoption/_story.md)
-- [ ] [04 — Major-bump re-evaluation flow](04-major-bump-reevaluation/_story.md)
-- [ ] [05 — Trace revalidation workflow](05-trace-revalidation-workflow/_story.md)
-- [ ] [06 — CodeQL workflow + pnpm audit signatures](06-codeql-and-audit-signatures/_story.md)
-- [ ] [07 — Gitleaks pre-commit hook](07-gitleaks-precommit/_story.md)
-- [ ] [08 — Sandcastle reviewer prompt update](08-reviewer-prompt-update/_story.md)
-- [ ] [09 — CI security guide + CLAUDE.md](09-ci-security-guide-and-docs/_story.md)
+- [x] [01 — Trace schema extensions (socketRisk + lastRevalidated)](01-trace-schema-extensions/_story.md)
+- [x] [02 — Socket integration (skill + CI)](02-socket-integration/_story.md)
+- [x] [03 — Renovate adoption](03-renovate-adoption/_story.md)
+- [x] [04 — Major-bump re-evaluation flow](04-major-bump-reevaluation/_story.md)
+- [x] [05 — Trace revalidation workflow](05-trace-revalidation-workflow/_story.md)
+- [x] [06 — CodeQL workflow + pnpm audit signatures](06-codeql-and-audit-signatures/_story.md)
+- [x] [07 — Gitleaks pre-commit hook](07-gitleaks-precommit/_story.md)
+- [x] [08 — Sandcastle reviewer prompt update](08-reviewer-prompt-update/_story.md)
+- [x] [09 — CI security guide + CLAUDE.md](09-ci-security-guide-and-docs/_story.md)